Strawberry tree (Arbutus unedo), a native species in southern Europe and Ireland. The sweet, mealy fruits are eaten raw and are made into sherberts, preserves and alcoholic drinks. It is closely related to the madrone tree (A. menziesii) of the Pacific coastal region of the U.S. The Mexican species Arbutus glandulosa cv. 'marina' also grows in the Arboretum. It has a smooth, reddish exfoliating bark similar to the Pacific madrone.

Two members of the aralia family (Araliaceae). Left. Queensland umbrella or octopus tree (Schefflera actinophylla). Right: Tupidanthus calyptratus with multiple trunks bearing cauliflorous fruits. Another interesting member of this family in the Palomar College Arboretum is the spiked cabbage tree (Cussonia spicata) native to South Africa.

The large tree is a hybrid between the Peruvian species Phytolacca weberbaueri and the Argentine ombu tree (P. dioica). In the distance is the Palomar "P" on the southwest slope of Owens Peak. Unlike the blue-gray granite bedrock on the Palomar College campus, the summit of Owens Peak is composed of Santiago Peak Volcanic rock. This dark, fine-grained, very hard rock dates back to the Jurassic Period, 135-180 million years ago, to a time when dinosaurs walked the earth. This heavy rock is resistant to erosion and forms some of the higher topography in coastal San Diego County.

Massive trunk and base of another Phytolacca weberbaueri in the Palomar College Arboretum. This tree came from a viable seed from one of the large parental trees. It might be a hybrid (P. weberbaueri x P. dioica). The American wild vegetable called pokeweed (P. americana) is related to these huge trees.

Eucalyptus caesia, showing woody burl (lignotuber) at the base of multiple trunks. Burl-forming trees and shrubs of Australia can resprout after fire, like many shrubs of the local chaparral and coastal sage scrub in southern California.

A young lemon-scented gum (Eucalyptus citriodora) showing a small developing lignotuber. This species reproduces by seedlings near the top of the Arboretum hill. Another common seedling Eucalyptus at the top of hill is the red gum (E. camaldulensis).

Gum kino oozing from a fissure in the trunk of a lemon-scented gum (Eucalyptus citriodora). Chemically the eucalyptus "gums" are rich in tannins (kinotannic acid) and are similar to another phenolic compound called catechu. They are known in the trade as kinos or gum kinos and are used as tannins to convert animal hide into leather. One of the main Australian sources of kino is the common red gum (Eucalyptus camaldulensis), naturalized throughout San Diego County. Kino gums are also used medicinally as astringents to relieve throat irritation, dysentery and diarrhea. True polysaccharide gums, such as locust bean gum from the carob tree (Ceratonia siliqua), and chicle, a terpene gum from the latex sap of the sapodilla tree (Achras zapota), are chemically quite different. They all probably serve to seal off wounds and prevent bacterial and fungal infections.

The buds and flowers of bushy yate (Eucalyptus lehmannii) grow out of the trunk and limbs, an adaptation known as cauliflory. This fast-growing Australian tree makes a dense, leafy barrier or screen in southern California.

The buds and flowers of bushy yate (Eucalyptus lehmannii) grow out of the trunk and limbs, an adaptation known as cauliflory. This fast-growing Australian tree makes a dense, leafy barrier or screen in southern California. It is a very successful tree in the Palomar College Arboretum.

The bisexual flowers of Eucalyptus polyanthemos showing the cylindrical cap (operculum) that separates to expose a mass of white stamens which surround the female pistil. The majority of flowering plant species have fewer than 20 stamens.

Left: The trunk of Mindanao gum (Eucalyptus deglupta), a species native to Mindanao in the Philippines. Right: The leaves of silver dollar gum (E. polyanthemos) and a beautiful bowl made from the heartwood.

Red ironbark (Eucalyptus sideroxylon), an Australian species with dark, thick bark and beautiful, reddish-brown heartwood. Several trees of this species grow in the hills adjacent to the Arboretum.

A. Angophora costata. B. Eucalyptus caesia. The seed capsules of Angophora have longitudinal ridges and calyx teeth that are lacking in the seed capsules of Eucalyptus.

Phoracantha recurva, a long-horned wood-boring beetle introduced into southern California from Australia. According to A. V. Evans and J. N. Hogue (Field Guide to Beetles of California, 2006), it was first discovered at the University of California at Riverside in 1995. As of June 2008, it has infested red gums of (Eucalyptus camaldulensis) near CSUSM in San Marcos. The larvae tunnel between the bark and wood, but construct their pupal chambers in the heartwood. Adult beetles are attracted to fallen branches and injured or water-stressed trees.

Two more members of the large and diverse myrtle family (Myrtaceae). Left: Pineapple guava (Feijoa sellowiana) native to South America. Right: Lemon bottlebrush (Callistemon citrinus) native to Australia.

Basswood Family (Tiliaceae)

The distinctive leaf-like bracts and fruits of the American linden (Tilia americana). Also known as basswood, prepared microscope slides of stem cross sections from this species are commonly used in general botany and plant anatomy classes.

Flower and spiny fruit of African linden (Sparmannia africana).

Magnolia Family (Magnoliaceae)

Left: Large blossom of the southern magnolia (Magnolia grandiflora). The numerous sepals and petals are called tepals because they are similar in size and shape. The conelike receptacle in the center is composed of numerous spirally arranged carpels and numerous spirally arranged stamens. The stamens have already fallen away in this photo, exposing the brown stalk (axis) of the receptacle. Right: Conelike receptacle bearing numerous follicles. Each follicle has split open and the seed has fallen out. Conelike fossils similar to magnolia receptacles have been discovered in ancient sedimentary strata, indicating that this is a primitive family.

Fragrant champaca (Michelia champaca), a primitive relative of the magnolia native to the Himalayas. Champaca oil used to make "Joy" perfume is distilled from the flowers. Like the magnolia, the conelike cluster of carpels in the center of flower mature into a cluster of seed-bearing follicles.